A large primate breeding colony, with a current average birth rate of 300 infants per year, and a spontaneous mortality of approximately 15-20 percent, will be closely observed to precisely determine the causes and epidemiology of sudden death. The colony is composed primarily of Macaca nemestrina species. Methods employed will include epidemiologic monitoring of all pregnancies, births and deaths, serial growth measurements, and analysis of variables in environment and diet which may affect the results. All deaths will be studied carefully at autopsy to determine the precise cause of death. These studies will include microbiological study immediately upon receipt of a case (viruses, bacteria, mycoplasma), and the results compared with the microbial flora of matched controls. The primary goal of this project is to determine a.) the precise causes of sudden death in infant primates and, b.) if a syndrome clinically and epidemiologically similar to sudden infant death syndrome (SIDS) in human infants occurs in primates. It is expected that the data will provide information leading to the development of an animal model of SIDS.